In the U.S. Pat. No. 3,714,815 disclosed for performing continuous measurements of coagulating liquids, preferably blood and derivatives thereof. Which apparatus has means for producing shearing and deformation effects in the coagulating fluid in the form of a circularly cylindrical beaker and a test member which also has a circularly cylindrical configuration and is suspended from a torsion wire and is located in the beaker. An annular gap between the beaker and the test member receives the fluid being measured. An orbital motion is imparted by appropriate means to the wall surfaces of the beaker which confine the fluid.
This apparatus is designed and adjusted such that the peripheral speed of the orbital movement substantially approximates the rate of flow of the blood in human blood vessels. In this patent, it has already also been proposed, inter alia, to produce the orbital movement by a rotating electrical field which correspondingly acts upon the beaker.
Thus, it has been known to measure the coagulation of blood by subjecting the fibrin, produced during coagulation, to a specific shearing stress. By appropriate metering of this shearing stress, the resilient resistance of the coagulum can be increased far more rapidly compared with an apparatus in which the fluid is not subjected to a metered shearing stress of this kind during coagulation, that is, during the formation of the coagulum. Thus, it is far simpler to distinguish between normal and pathological blood coagula than with the original apparatus described in the above patent. This renders it possible to provide a substantial improvement in the diagnostic routine. At the same time, it is possible to afford a sharp definition of the so-called coagulation time which elapses until the coagulum commences to form and which is normally difficult to define.